Red: This common colored light, processed from long wavelengths, is best for preserving your night vision because it doesn’t oversaturate your rods. So choosing between white and colored light lets us see our surroundings in different ways. Rods only respond in very dim light, whereas the three types of cones-respectively most sensitive to long, middle, and short wavelengths-do the work under normal circumstances. These photoreceptors are tuned to react to different wavelengths and operate under different lighting conditions. That process starts when the millions of rods and cones at the back of the eye absorb light. “It’s actually this quite elaborate, sophisticated operation of interpretation that the brain is doing.” in neurobiology and runs a National Institutes of Health–funded research lab that studies color and cognition. It’s not some reflex tied to wavelength,” explains Bevil Conway, who has a Ph.D. Understanding which is best for what purpose requires brushing up on your biology. Headlamps are often outfitted with multicolor LEDs. Coast and Ledlenser let you change the beam pattern from spot to flood by simply twisting or pulling the housing around the lens, making them easier to operate with gloved hands. Black Diamond and BioLite have memory functions that put the lamps in the most recently used brightness mode when you power them on. Petzl, for example, built a sensor into some of its models that automatically adjusts the beam’s brightness based on lighting conditions.
Pushed by the demands of backcountry hikers, climbers, ultra runners, and tradesmen, headlamp manufacturers have also developed smart features that give you greater control over the size and intensity of the beam to suit your needs.
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